Proximal Clot Research Articles

Prevention of venous thromboembolism

The aim of prophylaxis in venous thromboembolism is firstly to prevent fatal pulmonary embolism and secondly to reduce the morbidity associated with deep vein thrombosis and the post-phlebitic limb. Particularly high-risk groups are identifiable and include those over 60 years of age undergoing major surgery, patients with malignancy and those undergoing hip operations. Low-dose subcutaneous heparin (5000 U s.c. commenced two hours preoperatively and continued eight to twelve hourly until the patient is fully mobile) is unequivocally effective in preventing deep vein thrombosis in medical and surgical patients and, most importantly, significantly reduces the incidence of fatal postoperative pulmonary embolism and total mortality. Furthermore, in established deep vein thrombosis, low-dose heparin limits proximal clot propagation, which is the prelude to pulmonary embolism. Despite this, surveys have demonstrated an alarming deficiency amongst clinicians in the application of measures to prevent venous thromboembolism. Heparin prophylaxis carries a small risk of increased bleeding complications, mostly evidenced by the frequency of wound haematoma rather than major haemorrhage. Low molecular heparin fragments (e.g. Fragmin, Choay, Enoxaprin) are now emerging as useful alternative agents, having the advantage of once daily administration and yet providing similar efficacy in the prevention of deep vein thrombosis. However, protection against fatal pulmonary embolism has yet to be demonstrated. Mechanical methods of prophylaxis designed to counteract venous stasis, such as graduated elastic compression stockings, are also beneficial in protection against deep vein thrombosis but by themselves do not achieve such consistently good prophylaxis as low-dose heparin. However, clinical trials with combinations of mechanical methods and low-dose heparin indicate that this may be the optimum approach to very high-risk patients. In the presence of established acute deep vein thrombosis, anticoagulant therapy is the mainstay in preventing pulmonary embolism. Vena caval interruption procedures should be reserved for patients in whom anticoagulation is contraindicated or for those who develop recurrent pulmonary embolism despite adequate anticoagulation.

Congenital Hypoplasia of the Inferior Vena Cava: An Underappreciated Cause of Deep Venous Thromboses among Young Adults

This report illustrates how newer imaging techniques are identifying vasculopathies as risk factors for deep venous thrombosis (DVT). In this case, a healthy young man presented with a straightforward DVT but without traditional risk factors. Doppler ultrasonography confirmed a proximal clot, and contrast-enhanced computed tomography identified a hypoplastic inferior vena cava (IVC). DVTs cause considerable morbidity and death each year, including approximately 200,000 fatal pulmonary embolisms. Specific treatment of DVTs and long-term management and prevention strategies are contingent on the etiology, which can be determined in approximately 85% of cases. A hypoplastic IVC was discovered during efforts to find the cause of thrombosis, and a Medline search suggests that this anomaly should be considered for young persons with DVTs. DVTs are common and their underlying etiology should be identified to help guide long-term management. Evidence is emerging that an anomalous IVC should be ruled out as a cause of DVT among young patients.

The effect of intraoperative heparin administered during total hip arthroplasty on the incidence of proximal deep vein thrombosis assessed by magnetic resonance venography

Intraoperative, unfractionated heparin, administered intravenously before the femoral work, has demonstrated to be effective in reducing the strong thrombotic stimulus that occurs during total hip arthroplasty (THA) surgery. This randomized, double-blind, prospective study included only THA patients with significant comorbidities predisposing them to deep vein thrombosis (DVT). The 2 groups consisted of study patients who received a single dose of intravenous, intraoperative, unfractionated heparin and control patients who received a single dose of intravenous, intraoperative saline. Magnetic resonance venography was used as the DVT diagnostic tool. The overall prevalence of proximal femoral vein clots was 2.2% (3 of 134), whereas pelvic thrombosis was detected in 10.4% (14 of 134). This study demonstrated that pelvic thrombi may form following THA and that a single dose of intraoperative heparin does not prevent their formation, but may be effective at preventing ipsilateral femoral thrombi. This study strongly supports a multimodal approach to DVT prophylaxis following THA.

Transcatheter thrombolysis with high-dose bolus tissue plasminogen activator in iatrogenic arterial occlusion after femoral arterial catheterization.

To assess the efficacy of percutaneous local thrombolysis with high-dose bolus recombinant tissue plasminogen activator (rt-PA) in patients with acute limb ischemia due to arterial thrombosis after cardiac catheterization. We treated eight patients (7 men; mean age 56 years) with thrombotic occlusion of both the common femoral artery (CFA) and external iliac artery (EIA) in six patients and of the CFA only in two patients. Two 5 mg boluses of rt-PA were injected into the proximal clot through a 5 Fr end-hole catheter and subsequently two additional boluses of 5 mg rt-PA were given through a catheter with multiple side-holes. In case of a significant amount of residual thrombus, a continuous infusion of 2.5 mg/hr of rt-PA was started. Successful lysis was achieved in all patients. The mean duration of lysis was 2 hr 41 min. The mean total amount of rt-PA delivered was 23.16 mg. In four patients unmasked flow-limited dissections confined to the CFA were managed by prolonged balloon dilatation, while in the remaining four patients with extension of the dissection to the external iliac artery one or two Easy Wallstents were implanted. There was prompt relief of lower limb ischemic symptoms and signs in all patients. Two groin hematomas were conservatively treated. Clinical and color Doppler flow imaging follow-up with a mean duration of 15 months, showed no reappearance of ischemic symptoms or development of restenosis in any of the patients. One patient died 6 months after thrombolysis. Transcatheter thrombolysis with high-dose bolus rt-PA is a safe and effective treatment in patients with iatrogenic arterial occlusion after femoral catheterization. Underlying dissections should be treated by prolonged balloon dilatation but stent implantation is often required.

The Incidence of Deep Venous Thrombosis in ICU Patients

To determine the incidence, clinical presentation, and risk factors of deep venous thrombosis (DVT) in a high-risk group of ICU patients receiving DVT prophylaxis. A prospective cohort study. Two ICUs of a university-affiliated teaching hospital. Patients admitted to the ICUs within 48 h of hospitalization and who had an ICU stay of > or = 4 days underwent venous duplex scans. None. One hundred two patients were studied. Ninety-four (92%) patients received DVT prophylaxis. Twelve patients (12%) were documented to have DVT by venous duplex scans. There was proximal clot extension in eight of these patients, four of whom had high-probability ventilation/perfusion scans. Of the 56 patients without signs or symptoms of DVT, only two (3.6%) had abnormal scans. Leg swelling was present in 11 patients, six of whom had DVT (p = 0.004). One of 11 patients with unexplained fever had an abnormal scan. Five of the 26 patients (19%) receiving pneumatic compression developed DVT compared with five of 68 patients (7.4%) receiving subcutaneous heparin (not significant). No specific factor was identified that increased the risk of DVT. In this study, the incidence of DVT in a group of high-risk ICU patients receiving DVT prophylaxis was 12%. Since scans in patients without signs or symptoms suggestive of DVT were abnormal in only 3.6% of patients, venous scans should be performed only in patients with features suggestive of DVT or pulmonary embolism.

Deep venous thrombosis following total hip arthroplasty: Effects of prolonged postoperative epidural anesthesia

The authors studied the use of epidural anesthesia prolonged to 48 hours of epidural analgesia in 120 total hip arthroplasty patients in a case-control fashion. One half of the patients received prolonged epidural anesthesia, while the other matched half received general endotracheal anesthesia. Venograms were obtained after surgery and graded in blind fashion by a single radiologist. The overall incidence of deep venous thrombosis in the epidural versus general anesthetic groups was 23 (14 of 60 patients) versus 40% (24 of 60) ( P < .05). There was an identical incidence—8.3% (5 of 60 patients)—of proximal thrombosis in the two groups and all of the difference in the overall rates of thrombosis occurred in the calf. Fifteen percent (9 of 60 patients) of the epidural patients and 31.6% (19 of 60) of the general anesthetic patients demonstrated this finding ( P < .05). Of the 10 proximal clots, 8 (80%) were found in the operative leg, while only 29 (59.2%) of the 49 calf clots were found in the operative leg. Prolonged epidural anesthesia significantly decreases the incidence of deep venous thrombosis after total hip arthroplasty, with its most apparent benefit on calf vein thrombosis secondary to its hyperkinetic effect on lower limb blood flow. The observation that it has no demonstrable effect on the prevention of proximal thrombosis and our finding that the majority of proximal clots are in the operative leg suggest that thrombi in the thigh may be the result of a different primary pathogenic mechanism that is more related to endothelial injury than to changes in viscosity or blood flow. Epidural anesthesia alone does not address prevention of proximal thrombosis and therefore proper prophylaxis after total hip arthroplasty necessitates the concurrent use of additional methods.

Factors affecting deep vein thrombosis rate following total knee arthroplasty under epidural anesthesia

A retrospective review was performed of 448 consecutive patients undergoing primary, unilateral, bicondylar, and cemented total knee arthroplasty under epidural anesthesia by three surgeons to determine factors contributing to deep vein thrombosis rate. All had venography on the fourth or fifth postoperative day and received aspirin and elastic stockings as their only thromboprophylaxis. The overall deep vein thrombosis rate was 41% (2% had proximal clots). The rate of deep vein thrombosis was not related to obesity, history of heart disease, hypertension, prior malignancy, smoking, diagnosis of osteoarthritis, duration of surgery, type of local anesthetic used, or the use of postoperative epidural analgesia. The rate of deep vein thrombosis varied significantly between surgeons: one surgeon had an overall deep vein thrombosis rate of 58% (proximal thrombi, 4%) whereas the other two surgeons had a deep vein thrombosis rate of 35% (proximal clot thrombi, 1%). A number of possible mechanisms to explain the variation in deep vein thrombosis rates between surgeons are provided.

Predictive factors of effectiveness of streptokinase in deep venous thrombosis

In a prospective study, 174 patients (118 women and 56 men, average age 44 years, range 14 to 82) with proximal extensive thrombosis received streptokinase (100,000 U/hour) for an average of 2.8 days (range 0.5 to 7) through the catheter of a temporary caval fitter. Twenty-seven of 45 (60%) patients with nonocclusive clots were completely free of clots at the second phlebography versus 17 of 116 (14%) with occlusive clots (p < 0.001). Among nonocclusive clots, proximal ones (caval, iliac and femoral) were more easily lysed than popliteal clots (88 of 116 [76%] vs 26 of 58 [45%]; p < 0.001). In 41 of 132 (31%) patients, a daily injection of contrast medium through the filter-carrying catheter enabled the observation of a clot in the filter, which was lysed by streptokinase. Seventy patients with follow-up >2 years (median 34 months) were examined clinically. Nineteen of 22 (86%) patients with venograms free of clots at discharge were free of clinical sequelae versus 16 of 48 (33%) without normal venograms (p < 0.001). It is concluded that: (1) in the case of occlusive clots, only a few patients were normalized after streptokinase; (2) proximal nonocclusive clots were most effectively lysed; (3) when venograms were free of clots at discharge, the majority of patients did not have venous sequelae at follow-up; and (4) embolie migration seems to occur frequently with streptokinase.

Prevention of Thromboembolic Disease Following Total Knee Arthroplasty

Seventy-two patients were randomized into a prospective clinical trial to evaluate the effects of epidural (EA) versus general anesthesia (GA) on the incidence of thromboembolic disease (TED) following total knee arthroplasty (TKA). Males received aspirin 650 mg po bid and females low-dose warfarin daily to maintain the prothrombin time at 15 to 16 seconds for pharmacologic prophylaxis against TED. Thirty-four patients had EA and 38 GA for their primary TKA. Contrast venography and ventilation-perfusion scanning were performed on the sixth, seventh, and eighth postoperative days, and these were interpreted in a blinded fashion. The mean age of the 45 males and 27 females was 64 years (range, 42-84 years). There were no significant differences between the two groups with respect to hematocrit, operative time, blood loss, number of units transfused, or hospital stay. Twelve of the 34 patients (35%) receiving an EA and 10 of the 38 patients (26%) receiving GA developed TED, an overall incidence of 31% (p greater than 0.05) Fifty-three percent of the clots were located in the popliteal vein above the trifurcation or more proximal. However, the incidence of proximal vein thrombosis was significantly less in patients receiving an EA (46%) rather than a GA (64%). The incidence and distribution of clots was not affected by the type of pharmacologic prophylaxis, gender, or use of methylmethacrylate. Ten percent of the patients had a positive scan by strict criteria and were thought to have a pulmonary embolism (PE). In patients with a femoral vein clot, the incidence of PE was 67%. One bleeding complication occurred in a patient who took double the appropriate warfarin dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Prophylaxis of venous thromboembolism

The objective of prophylaxis in venous thromboembolism is, first, to prevent fatal pulmonary embolism and, second, to reduce the morbidity associated with deep vein thrombosis (DVT) and the postphlebitic limb. This should now be standard practice for most patients over 40 years of age undergoing major surgery and for younger patients with a history of venous thromboembolism. Particularly high-risk groups include patients over 60 years of age undergoing major surgery, those with malignancy, and those requiring hip operations. Low-dose subcutaneous heparin 5,000 IU commencing 2 hours preoperatively and continuing 12 hourly until the patient is fully mobile is unequivocally effective in preventing DVT in medical and surgical patients and, most importantly, significantly reduces the incidence of fatal postoperative pulmonary embolism and total mortality. Such prophylaxis, in the presence of established DVT, also limits proximal clot propagation, which is the precursor of major pulmonary embolism. Low-dose heparin prophylaxis is associated with a small risk of bleeding complications, evidenced mostly by an increased frequency of wound hematoma rather than major clinical hemorrhage. Low molecular weight heparin fragments (e.g., Fragmin, Choay, Enoxaparine) are emerging as useful alternative agents, having the advantage of once daily administration and yet providing similar efficacy in the prevention of DVT. Mechanical methods of prevention which counteract venous stasis, such as graduated elastic compression stockings, are also useful in protecting against DVT but have not been shown to prevent fatal postoperative pulmonary embolism. They are recommended particularly for patients in whom heparin prophylaxis is best avoided (e.g., neurosurgery) and possibly in combination with heparin in very high-risk patients.

Application of thrombolytic therapy in vascular occlusive disease: A surgical view

The use of fibrinolytic agents to control the fibrinolytic enzyme system and lyse pathologic fibrin deposits or thrombus has now assumed a position with anticoagulants and vascular surgery in the physician's therapeutic armamentarium. The principal exogenous activators that are used clinically are streptokinase, urokinase, and tissue plasminogen activator. Acute arterial occlusions are more likely than chronic occlusions to respond to thrombolytic therapy, especially if treatment is instituted within a few hours of onset of symptoms and if the disease is due to embolic material rather than in situ thrombosis. Since the duration of drug infusion necessary to lyse arterial thrombus cannot be predicted, patients in whom tissue viability cannot be determined or in whom ischemia cannot be tolerated during the drug infusion interval are not candidates for intraarterial fibrinolytic drug infusion. In treating patients with venous occlusion, thrombolytic therapy is more effective against proximal clots than in calf thrombosis. No protective effect from pulmonary embolism has been noted in trials comparing heparin with streptokinase. Fifty percent of patients with an initial episode of deep venous thrombosis treated within 72 hours of onset will have complete resolution of thrombus with preservation of valve function.